The first question is not simply which island to choose, but what kind of Greece you want to experience.
Athens works well as an introduction, combining ancient landmarks with a lively modern food and hotel scene. The Peloponnese is ideal for travellers who want history, coast, countryside and a slower touring rhythm, while northern Greece and Meteora bring monasteries, mountains, wine regions and a more dramatic mainland landscape. Crete should often be treated almost as a country within the country. It has cities, beaches, mountains, villages, archaeological sites, walking routes and a strong food culture, making it one of the best choices for a complete trip without too much moving around.
Once the region is right, the hotel or villa should support the rhythm of the holiday, whether that is simple and slow, polished and romantic, family-friendly or built around food, sea and landscape.